1. Field of the Invention
The present invention relates to a sealing device sealing a shaft periphery and the like of a portion which tends to be exposed to a muddy water or the like from an external portion, such as a transfer apparatus, a wheel bearing apparatus and the like of a vehicle, and more particularly to a sealing device provided with a structure preventing the muddy water or the like from making an intrusion into a sliding section of an oil seal lip.
2. Description of the Conventional Art
In a sealing device used for a transfer apparatus, a wheel bearing apparatus and the like of a vehicle, since a muddy water or the like tends to come in from an external portion, it is necessary to inhibit the muddy water or the like from making an intrusion into a sliding section of an oil seal lip as much as possible, thereby preventing a reduction of a sealing performance of the oil seal lip as much as possible. FIG. 2 is a half sectional view of an installed state and shows an example of this kind of sealing device in accordance with a conventional art by cuffing along a plane passing through an axis O.
In particular, in FIG. 2, reference numeral 2 denotes a housing of a transfer apparatus, reference numeral 3 denotes a rotating shaft which is inserted to the housing 2 and is supported in a state of being rotatable around an axis O via a bearing 4, reference numeral 5 denotes a sleeve which is spline fitted to an outer periphery of the rotating shaft 3 and is fixed by a nut 6, and reference numeral 7 denotes a packing which seals between the rotating shaft 3 and the sleeve 5. A companion flange 5a formed at an end portion of the sleeve 5 is connected to a propeller shaft (not shown) or the like.
A sealing device 100 is provided with a non-rotating oil seal 110 which is positioned at an outer side in an axial direction of the bearing 4 and is attached to an inner periphery of the housing 2, and a slinger 120 which is positioned at an outer side in an axial direction of the oil seal 110, is attached to an outer periphery of the sleeve 5, and is rotated integrally with the rotating shaft 3 and the sleeve 5.
Describing in detail, the oil seal 110 has an oil seal lip 111 which extends toward the bearing 4 side, and a side lip 112 which extends toward an opposite side (an outer side) to the oil seal lip 111. The oil seal lip 111 is structured such as to prevent a lubricating oil fed to the bearing 4 from leaking by being slidably brought into close contact with an outer peripheral surface of the sleeve 5, and the side lip 112 is structured such as to prevent a muddy water or the like coming in from an external portion A from making an intrusion into the oil seal lip 111 side by being slidably brought into close contact with a flange section 121 of the slinger 120. The slinger 120 itself has a throwing off action on the basis of centrifugal force generated in the flange section 121, and achieves an improvement of an effect of preventing the muddy water or the like from making an intrusion, by making an outer tube section 122 thereof to be near to an end portion of the housing 2 (refer, for example, to the following patent documents 1 to 3), or providing a conical tubular dust lip, in which a leading end has a large diameter, on a radially outer end portion of the slinger 120 and bringing it slidably into close contact with a radially outer edge portion of the housing 2 (refer, for example, to the following Japanese Utility Model Publication No. 7-33017).
Reference is made to Japanese Unexamined Patent Publication No. 2006-9930, Japanese Unexamined Utility Model Publication No. 5-54871, Japanese Unexamined Utility Model Publication No. 3-67765, and Japanese Utility Model Publication No. 7-33017.
However, in accordance with the sealing device 100 as shown in FIG. 2 (refer to Japanese Unexamined Patent Publication No. 2006-9930, Japanese Unexamined Utility Model Publication No. 5-54871 and Japanese Unexamined Utility Model Publication No. 3-67765), if a gap between the outer tube section 122 of the slinger 120 and the outer peripheral surface of the end portion of the housing 2 is made small, there is a risk that the outer tube section 122 comes into contact with the outer peripheral surface of the end portion of the housing 2 on the basis of a working tolerance, an eccentricity of the rotating shaft 3 or the like, so that it is not possible to make the gap sufficiently small. Therefore, it is impossible to sufficiently prevent the muddy water or the like from making an intrusion.
Further, as for the sealing device in which the radially outer end portion of the slinger 120 is provided with the conical tubular dust lip in which the leading end has the large diameter as shown in patent document 4, since a body portion of the dust lip comes into close contact with a radially outer edge of an opening end of the housing 2, it is not possible to obtain a sufficient fastening margin with respect to the housing 2, and particularly in the case that the sealing device is submerged in the muddy water at a time of traveling on a punishing road, it is hard to inhibit the muddy water from making an intrusion. Further, in order to improve a muddy water sealing performance, there can be considered to increase the number of the side lip 112 and the dust lip, however, in this case, not only the sealing device 100 is enlarged in size, but also there is a risk that a specific fuel consumption is lowered by an increase of sliding torque.